The present invention relates generally to the asphalt pavement industry and, more particularly, relates to apparatus and methods of surfacing and resurfacing roadways or other pavement surfaces.
Roadway surfaces are usually paved. In the construction of new roadways, pavement is typically applied to an unpaved base after it has been graded and compacted. Over time, existing roadways inevitably become worn and in need of repair. For example, cracks can develop in the roadway surface, and/or the surface can become overly smooth. If cracks develop, the surface is no longer water resistant, and the roadway will deteriorate at an accelerated pace. If the surface becomes overly smooth, the skid resistance and traction for vehicles are diminished.
A common practice for maintaining roadway surfaces is through a practice known as xe2x80x9cchipsealingxe2x80x9d. Current chipsealing processes utilize an asphalt distributor vehicle for applying asphalt binder material (e.g., liquid asphalt, emulsified asphalt, molten bituminous material, asphalt binder material, etc.) and a subsequent chipspreader vehicle for distributing aggregate material (e.g. gravel, sand, crushed stone, recycled glass, etc.). Thus, in practice, chipsealing is performed by two separate vehicles making two separate passes over the same portion of the roadway in order to apply a single layer of pavement to that portion.
Chipsealing is a relatively fast and inexpensive technique for surfacing or resurfacing a roadway. However, presently-employed chipsealing processes have several deficiencies as will be detailed below.
The surface produced by the binder and the stone is often desired to be about one stone thick. In practice, however, additional stone is applied beyond what is required to produce a layer one stone thick in order to keep the tires of the chipspreader from picking up stones off the freshly laid surface. This results in extra stone being required which is expensive from a materials standpoint. In normal operation, the application process is stopped and restarted quite often in order to re-supply stone and asphalt binder to the process. Stopping and restarting usually creates a bump or flaw in the surface, which is often unacceptable for high volume traffic, thus often limiting application of the chipsealing process to low volume traffic applications.
Another problem with two separate machines is that it is difficult to properly control the time between the application of the asphalt binder and the aggregate material. It is necessary to control proper spacing between the asphalt distributor vehicle and the chipspreader vehicle. If the timing is not closely controlled or there is a problem with one vehicle, the binder can begin to set or cure before the aggregate is applied. This reduces the effectiveness of the binder in holding the aggregate to the road surface and may cause dislodging of stones by subsequent traffic.
It is a primary objective to provide a solution to the stopping and restarting problems associated with current chipsealing processes which can cause bumps or flaws in a finished road surface.
It is another objective of the present invention to provide a chipsealing apparatus and method that may reduce the amount of aggregate material needed to effect the desired surfacing or re-surfacing of a roadway surface.
It is another objective of the present invention to provide a chipsealing apparatus and method that may operate at a maximum speed that is at least substantially the same as current chipsealing processes or is otherwise economically feasible.
In accordance with these and other objectives, the present invention is directed toward a novel roadway paving vehicle that may be used for chipsealing paving operations. It comprises both an asphalt binder material dispensing system and an aggregate material system on the same apparatus. The asphalt binder material and aggregate material are not mixed inside the apparatus prior to discharge. The roadway paving vehicle has an engine and wheels with opposed front and rear ends. The aggregate material dispensing system comprises an input hopper disposed proximate the front end of the vehicle that receives aggregate material, an output hopper disposed proximate the rear end of the vehicle, and a conveyor mechanism extending between the input hopper and the output hopper. The conveyor mechanism transports aggregate material from the input hopper to the output hopper. The output hopper converges toward a discharge port to discharge aggregate material over the ground surface. The asphalt binder material dispensing system comprises a tank for holding asphalt binder material, a spray bar between the discharge port and the front end, and a pump mechanism adapted to pump asphalt binder material from the tank to the spray bar. The spray bar has a plurality of nozzles that spray the asphalt binder material.
The present invention is also directed toward a method of chipsealing a roadway surface with a roadway paving vehicle. The method comprises storing a supply of asphalt binder material in a tank on the roadway paving vehicle; transporting asphalt binder material from the tank to a spray bar at the rear end of the roadway paving vehicle; spraying asphalt binder material from the spray bar at a first span over the roadway surface forming a layer of asphalt binder material on the roadway surface; storing a supply of aggregate material in an input hopper at the front end of the roadway paving vehicle; transporting aggregate material from the input hopper to an output hopper at the rear end of the roadway paving vehicle; discharging aggregate material from the output hopper at a second span over the layer of asphalt binder material; and preventing intermixing of asphalt binder material and aggregate material prior to the discharging of aggregate material and spraying of asphalt binder material.
The present invention is also directed toward a novel supply truck for connection to another vehicle or apparatus. The truck includes a chassis supported on wheels extending between front and rear ends. A supply hopper is supported by the chassis and has a discharge region at the rear end. A conveyor mechanism in the supply hopper conveys aggregate material toward the discharge region. A tailgate closes the discharge region of the supply hopper. The tailgate can move rearwardly relative to the chassis to open the discharge region to allow discharge of aggregate material from the rear end of the supply truck. The supply truck further includes a supply tank carrying liquid material (such as asphalt binder material for example). A transfer conduit is connected to the supply tank and is carried by the tailgate. The transfer conduit includes a hydraulic coupling that extends rearwardly when the tailgate moves rearwardly. It is used to transfer liquid such as binder. It may also support electronic controls if desired.
It is an aspect of the invention to provide a supply truck with a live bottom hopper having a supply tank carrying liquid material in which the supply tank is disposed beneath the conveyor mechanism and the hopper and between the front wheel set and the rear wheel sets, whereby a low center of gravity is provided when the tank is filled with liquid.
It is a further aspect of the present invention to provide a new roadway paving system comprised of a roadway paving vehicle and a supply truck wherein the system may be operated on a continuous basis. This is accomplished with a linking system between the supply truck and roadway paving vehicle. The two vehicles can be linked and unlinked during continuous operation without stopping with the roadway paving vehicle storing sufficient amounts of asphalt binder material and aggregate material on the roadway paving vehicle for application between supply truck changes.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.